Construction method to control front engine compartment deformation

ABSTRACT

A frame structure absorbs energy from frontal impacts and extends under a front portion of the body frame. The frame structure includes a rear sub-frame located below and in front of a pair of side frame under-members, and an inverter protection brace extending between the front sub-frame and the rear sub-frame. Loading from the inverter protection brace travels through the rear sub-frame to A-point bolt connections located on the pair of front frame side members. The rear sub-frame moves rearward and deforms at the A-point bolt connections. The load through the A-point bolt connections changes the deformation mode of the frame front side members between the A-point bolt connections and B-point bolt connections. At least one of the pair of side frame under-members buckles rearward of the B-point bolt connection located on the pair of side frame under-members for energy absorption during the frontal impact.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related by common subject matter to U.S. patentapplication Ser. No. 13/445,138; Ser. No. 13/445,157; Ser. No.13/445,169; Ser. No. 13/445,176; and Ser. No. 13/445,191, all filed onApr. 12, 2012, which are incorporated by reference herein in theirentirety.

FIELD OF THE INVENTION

The invention relates to a land vehicle having supporting wheels toengage a surface over which the vehicle moves, a motor or hybridelectric engine enabling the vehicle to be moved along the surface, aframe providing support for a vehicle body, where at least a portion ofthe frame permanently changes shape or dimension in response to impactof the frame with another body, and more particularly to a body framefor an electric vehicle having structural members adapted to absorbenergy from frontal impacts which extend under a front portion of thebody frame, including structure for retarding motion by positiveengagement of elements, where relatively at least one member is adaptedto be deformed beyond its elastic limit to restrain relative motion.

BACKGROUND

During frontal impacts defined in Insurance Institute for Highway Safety(IIHS) and Federal Motor Vehicle Safety Standard (FMVSS) protocols,front structural members deform into the engine/motor compartment andbody cabin. In these areas, electric or hybrid electric vehicles willhave high voltage (HV) components (e.g. an inverter in the motorcompartment and a battery under the body cabin, DC-DC converter,charger). These parts may be positioned in a traditional crush zoneand/or a new crush zone presented by the removal of the much largerinternal combustion engine and supporting structures.

High voltage (HV) inverters are typically protected by a thick case toresist any crushing force or packaged outside of the expected crushzone. High voltage (HV) batteries are typically packaged outside oftraditional crush zones to avoid deformation of battery arrays. Removalof traditional load paths result in increased body cabin deformationunless appropriate alternative structures are added.

The large mass for an inverter case is counter-productive for a longrange electric vehicle (EV). Thus a more mass effective option isneeded. Battery arrays packaged outside of a crush zone are typicallysmaller and thus limit drivable range for the vehicles. Overall, allhigh voltage (HV) components must be protected from damage during crashimpacts while maximizing drivable range through larger batteries and lowmass protection structures.

SUMMARY

A frame structure for a land vehicle has wheels to engage a surface overwhich the vehicle moves. An electric motor enables the vehicle to bemoved along the surface. The frame structure provides support for avehicle body. At least a portion of the frame structure permanentlychanges shape in response to impact of the frame structure with anotherbody. The frame structure is adapted to absorb energy from frontalimpacts. The frame structure extends under a front portion of the bodyframe. The frame structure includes a front sub-frame and a rearsub-frame located below and in front of a pair of side frameunder-members, and an inverter protection brace extending between thefront sub-frame and the rear sub-frame for transferring energy from thefront sub-frame to the rear sub-frame during a frontal impact.

A method is disclosed of assembling structural members for absorbingenergy from frontal impacts of a frame structure. The frame structurepermanently changes shape in response to impact of the frame structurewith another body. The frame structure extends under a front portion ofthe body frame. The method includes locating a front sub-frame and arear sub-frame below and in front of a pair of side frame under-members,and connecting an inverter protection brace extending between the frontsub-frame and the rear sub-frame for transferring energy during afrontal impact.

A frame structure is adapted to absorb energy from frontal impacts. Theframe structure extends under a front portion of the body frame. Theframe structure includes a rear sub-frame located below and in front ofa pair of side frame under-members, and an inverter protection braceextending between the front sub-frame and the rear sub-frame fortransferring energy from the front sub-frame to the rear sub-frameduring a frontal impact.

Loading from the inverter protection brace can travel through the rearsub-frame to an A-point bolt connection located on a pair of front frameside members. The rear sub-frame moves rearward and deforms at theA-point bolt connections. The load through the A-point changes thedeformation mode of the frame front side members between the A-point andthe B-point bolt connections. At least one of a pair of side frameunder-members buckles rearward of the B-point bolt connection to thepair of side frame under-members for energy absorption during thefrontal impact. The inverter protection brace can deform adjacent abolted connection at a rear end to form a safety cage around an inverterduring the frontal impact. A gusset connecting a front of the inverterprotection brace to the front sub-frame can rotate below the frontsub-frame to delay loading of the inverter protection brace and to delaybending of the front frame side members to improve energy absorption ofthe front frame side members during frontal impacts.

Other applications of the present invention will become apparent tothose skilled in the art when the following description of the best modecontemplated for practicing the invention is read in conjunction withthe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The description herein makes reference to the accompanying drawingswherein like reference numerals refer to like parts throughout theseveral views, and wherein:

FIG. 1 is a bottom view of a front end of a vehicle having front andrear sub-frames and a pair of side frame under-members, an inverterprotection brace extends between the front and rear sub-frames,reinforcement brackets are attached to the pair of side frameunder-members, ramps are connected to the reinforcement brackets, and atether is connected between the pair of side frame under-members and therear sub-frame;

FIG. 2 is a perspective view of a top of the rear sub-frame withattached structure, such as a steering gear, and depicts an A-point boltconnection location and a B-point bolt connection location;

FIG. 3 is perspective view of a bottom of the pair of side frameunder-members showing B-point bolt connection locations in phantom andreinforcement brackets attached to the pair of side frame under-members;

FIG. 4A is a perspective view of a passenger side reinforcement bracket;

FIG. 4B is a bottom view of the passenger side reinforcement bracket ofFIG. 4A;

FIG. 4C is a front view of the passenger side reinforcement bracket ofFIGS. 4A-4B;

FIG. 4D is a side view of the passenger side reinforcement bracket ofFIGS. 4A-4C;

FIG. 5A is a perspective view of a driver side reinforcement bracket;

FIG. 5B is a bottom view of the driver side reinforcement bracket ofFIG. 5A;

FIG. 5C is a front view of the driver side reinforcement bracket ofFIGS. 5A-5B;

FIG. 5D is a side view of the driver side reinforcement bracket of FIGS.5A-5C;

FIG. 6 is perspective view of a bottom of the pair of side frameunder-members showing ramps attached to the reinforcement brackets;

FIG. 7A is a perspective view of a passenger side ramp;

FIG. 7B is a bottom view of the passenger side ramp of FIG. 7A;

FIG. 7C is a front view of the passenger side ramp of FIGS. 7A-7B;

FIG. 7D is an inboard side view of the passenger side ramp of FIGS.7A-7C;

FIG. 7E is an outboard side view of the passenger side ramp of FIGS.7A-7D;

FIG. 8A is a perspective view of a driver side ramp;

FIG. 8B is a bottom view of the driver side ramp of FIG. 8A;

FIG. 8C is a front view of the driver side ramp of FIGS. 8A-8B;

FIG. 8D is an outboard side view of the driver side ramp of FIGS. 8A-8C;

FIG. 8E is an inboard side view of the driver side ramp of FIGS. 8A-8D;

FIG. 9A is a perspective view of a bottom of the front and rearsub-frames showing the inverter protection brace connecting the frontand rear sub-frames;

FIG. 9B is a perspective view of a top of the inverter protection braceof FIG. 9A showing a gusset on a front end and a bolted connection on arear end;

FIG. 10A is a perspective view of a top of the tether;

FIG. 10B is a bottom view of the tether of FIG. 10A;

FIG. 10C is a side view of the tether of FIGS. 10A-10B;

FIG. 11A is a simplified side view of front end of a motor vehicleillustrating an inverter, side frame under-member, inverter protectionbrace, reinforcement bracket, ramp, rear sub-frame, and steering gear attime zero prior to a frontal impact;

FIG. 11B is a simplified side view of front end of a motor vehicleillustrating an inverter, side frame under-member, inverter protectionbrace, reinforcement bracket, ramp, rear sub-frame, and steering gear at44 milliseconds (ms) time after a frontal impact, where the inverterprotection bracket hits a wall, the front sub-frame starts deformation,and a pocket starts to form;

FIG. 11C is a simplified side view of front end of a motor vehicleillustrating an inverter, side frame under-member, inverter protectionbrace, reinforcement bracket, ramp, rear sub-frame, and steering gear at68 milliseconds (ms) time after a frontal impact, where the rearsub-frame approaches the ramp, maximum front sub-frame crush occurs asthe inverter protection brace rotates under the attachment knuckle andloads wall directly, back side of pocket releases B-point connection ofrear sub-frame, tether loading begins, and ramp slide begins, whereloading through the inverter protection brace and rear sub-frameA-points allows front frame side member to deform between the A and Bpoints (not shown);

FIG. 11D is a simplified side view of front end of a motor vehicleillustrating an inverter, side frame under-member, inverter protectionbrace, reinforcement bracket, ramp, rear sub-frame, and steering gear at76 milliseconds (ms) time after a frontal impact, where tether releases,rear sub-frame is crushed to maximum amount, and ramp slide picks up,and the rear sub-frame detaches from the front frame side member at thetime of tether separation;

FIG. 11E is a simplified side view of front end of a motor vehicleillustrating an inverter, side frame under-member, inverter protectionbrace, reinforcement bracket, ramp, rear sub-frame, and steering gear at100 milliseconds (ms) time after a frontal impact, where loading ofsteering gear starts, ramp slide approaches maximum, additional loadthrough ramp initiates under-member weld separation, and inverter showsminimal damage;

FIG. 12 is a simplified graph showing an approximated IIHS ODB responseforce in kiloNewton (kN) versus stroke in millimeter (mm), where thedouble dashed line illustrates a strongly connected inverter protectionbrace to the front sub-frame (no rotation at knuckle resulting in earlycollapse of the front frame side member behind the A-point), a hard rampwith slide (i.e. easily separating B-point bolt connection), the solidline illustrates a strong yet deformable attachment for the inverterprotection brace (delays front frame side member collapse), areinforcement bracket forming an energy absorption pocket in the sideframe under-member in combination with a ramp and a steering gearcatcher, and the single dashed line illustrates a high massed initialvehicle with a strong yet deformable attachment for the inverterprotection brace, a reinforcement bracket forming an energy absorptionpocket in the side frame under-member in combination with a ramp, asteering gear catcher and a tether;

FIG. 13A is a detailed view of a side frame under-member, reinforcementbracket, and B-point attachment location, where movement of the rearsub-frame is shown in various time segments corresponding to FIGS.11A-11E (i.e. t=0 ms; t=44 ms; t=68 ms; t=76 ms; t=100 ms) during energyabsorption pocket formation;

FIG. 13B is a cross sectional view of the side frame under-member,reinforcement bracket, and B-point attachment taken as shown in FIG.13A;

FIG. 14A is a simplified schematic of a tether and rear sub-frame, wherea rotational arrow is shown for the tether in response to rearwardmovement of the rear sub-frame; and

FIG. 14B is a simplified schematic of a ramp, rear sub-frame and arotational arrow for the tether in response to rearward movement of therear sub-frame, where a combined rotational path defines a progressivelynarrowing gap between the rear sub-frame and ramp, such that D₀>D₁>D₂,increasing crushing contact and friction.

DETAILED DESCRIPTION

The purpose of the construction method and the vehicle frame structure10 is to protect the high voltage (HV) inverter 12 in the motorcompartment 14 and the HV battery array (battery) 16 under the bodycabin 18 from deformation and damage during a frontal impact event. Inaddition, the body deformation is controlled such that the body cabin 18maintains suitable clearance for occupants. The construction method andframe structure 10 will allow the high voltage (HV) inverter 12 to beprotected by a safety cage 20. The previously know safety cage wastypically large mass or approximately ten kilograms (kg), where are thesafety cage of the disclosed frame structure 10 may be only fivekilograms (kg). The inverter 12 can be placed in traditional frontalimpact crush zones with the disclosed construction method. The battery16 is able to be packaged in a traditional crush zone by deflecting thepath of intruding structures beneath the battery and by improving theenergy absorbing characteristics of the deforming system in this area.By controlling body cabin 18 deformation, by maintaining energyabsorption (EA), and by adding new load paths, the standard of safetyfor electric or hybrid-electric vehicles (Federal Motor Vehicle SafetyStandards (FMVSS) and Insurance Institute for Highway Safety (IIHS)tests) is maintained to a similar level as traditional internalcombustion (IC) engines.

Development of the frame structure system revolved around five concernsto be addressed. First, the high voltage (HV) inverter 12 is packaged ina traditional crush zone. To protect the high voltage inverter 12, asafety cage 20 needs to be established around the location of theinverter 12. An inverter protection brace 22 can be added to connect afront support structure (sub-frame) 24 to a rear sub-frame 26. The rearsub-frame 26 attaches at A-point bolt connections 56 a, 56 b and B-pointbolt connections 34 a, 34 b. The inverter protection brace load throughthe A-point bolt connections 56 a, 56 b changes the deformation mode ofthe front frame side members between the A-point bolt connections 56 a,56 b and the B-point bolt connections 56 a, 56 b. Loading from theinverter protection brace 22 travels through the rear sub-frame 26 tothe A-point bolt connections 56 a, 56 b located on a pair of front frameside members 50 a, 50 b resulting in earlier front frame side memberdeformation. Protection space is secured with the inverter protectionbrace 22, but as a result of the inverter protection brace directloading of the barrier wall and additional deformation of the frontframe side members the rear sub-frame 26 rearward displacement isincreased. Second, the increase in rear sub-frame 26 rearwarddisplacement results in intrusion into a support tray for the battery16. The trajectory of the rear sub-frame 26 can be changed by addingbody and/or sub-frame ramps 28 a, 28 b. The initial concept succeeds inlowering a path of the rear sub-frame 26 below the modules of thebattery 16, but effectively removes a load path through the batterysupport from the frontal impact structure resulting in increased bodycabin 18 deformation. Third, deflection of the rear sub-frame 26 belowthe battery 16 removes that load path (and in conjunction with removalof the traditional internal combustion (IC) engine) results inadditional body cabin 18 deformation from the loss of that EA member. Areinforcement bracket 30 a, 30 b can be added to the side frame undermembers 32 a, 32 b behind a B-point connection connections 34 a, 34 bwith enough clearance to facilitate formation of a pocket 36 a, 36 b toform during rear sub-frame 26 rearward motion. In conjunction with thefront frame side member deformation between the A and B pointconnections the rear sub-frame 26 deforms at the A-point boltconnections 56 a, 56 b and at least one of the pair of side frameunder-members 32 a, 32 b buckles rearward of the B-point boltconnections 34 a, 34 b for energy absorption during frontal impacts. Apocket 36 a, 36 b is formed, reinforced by added bracket, in the sideframe under-members 32 a, 32 b creating good energy absorption (EA) andthe resulting temporary lockup with reinforcement bracket brackets 30 a,30 b deforms the side frame under-members 32 a, 32 b rearward.Eventually, the pocket 36 a, 36 b breaks, releasing the B-point;attachment bolt connections 34 a, 34 b, and sliding movement of the rearsub-frame 26 relative to the side frame under-members 32 a, 32 b begins.Further improvement can be provided at the point where energy absorption(EA) drops corresponding to the beginning of rearward sliding movementof the rear sub-frame 26. Fourth, when the rear side of the pockets 36a, 36 b breaks, a force drop occurs corresponding to free rear sub-frame26 slide. In order to limit the drop in EA from free rear sub-frame 26slide a catch and engage system can be provided. A front edge orcatching surface 38 of the ramp 28 a can be aligned with a steering gear40 and B-point bolt connection 34 a. The front edge 38 of the ramp 28 acan be changed to act as a stopper or catcher for the steering gear 40.The steering gear 40 loads the ramp 28 a directly and then the sideframe under-member 32 a welds begin to separate rearward to mitigateforce levels. The locked together rear sub-frame 26 and catching featuresurface 40 move rearward in tandem with under-member weld separation.This improves the energy absorption (EA) condition until the rearsub-frame 26 slips-off. Fifth, it would be desirable to prevent earlyrear sub-frame 26 slip-off of the ramps 28 a, 28 b and the side frameunder-members 32 a, 32 b. A tether 44 can be added by modification of anoise-vibration (NV) and ride & handling brace to support the rearsub-frame 26 upward into energy absorption (EA) structures during arearward stroke. The rear sub-frame 26 slip can be delayed until almostall energy from a frontal impact is absorbed. The rear sub-frame 26locus is still beneath battery 16. The frame structure can be generallydefined in the field as either a uni-body construction where the framemembers provide support for a body cabin welded to the frame, abody-on-frame design where the cabin is fastened to the frame structure,or other variants (such as monocoche structures).

The frame structure system has five components which can be usedindividually or in any combination. First, the inverter protection brace22 can be connected to the front sub-frame 24 and the rear sub-frame 26,which protects the inverter 12 by establishing the strong safety cage20. Second, the addition of the body ramps 28 a, 28 b deflect the rearsub-frame 26 path beneath the battery 16, but increases the rearsub-frame 26 motion (from increased mass, and/or removal of thetraditional internal combustion (IC) engine load path, and/or increasedinput load from motor mount or brace structure) because no load isapplied to a frame of the battery 16 and the effect of ramping reducesthe natural tendency for rear sub-frame to body interference. Third, thereinforcement brackets 30 a, 30 b can be added on the vehicle side frameunder members 32 a, 32 b positioned rearward of the rear sub-frame 26attachment point. The rear sub-frame 26 is driven rearward against theside frame under-member members 32 a, 32 b deforming the side frameunder-member members 32 a, 32 b and creating the pocket 36 a, 36 b ofshape which is defined by the position of the reinforcement bracketwhich absorbs energy and slows the vehicle. After the rear sub-frame 26fully deforms the pockets 36 a, 36 b, the pockets 36 a, 36 b and tearsthe rear sub-frame 26 is released. Fourth, the catching surface 38 canbe added on the ramps 28 a, 28 b to allow catching of the steering gear40, which is mounted on the top surface of the rear sub-frame 26. Thecatching of the steering gear 40 in conjunction with the pockets 36 a,36 b allows more energy absorption to occur as the side frameunder-members 32 a, 32 b welding begins to separate from the vehicle asthe locked structure moves rearward. The rear sub-frame 26 slips at alater timing than without this catching surface 38. Fifth, bodynoise-vibration (NV) and ride-and-handling braces can be modified to actas the sub-frame tether 44. This tether 44 is able to control the rearsub-frame 26 motion such that additional crush is required to advancethe rear sub-frame 26 rearward. The tether 44 separates after most ofthe energy is removed from the system. In some cases it may bebeneficial to keep the tether 44 attached to prevent release of freeparts from the vehicle during a crash.

Referring now to FIGS. 1, 9A-9B and 11A-11E, the inverter protectionbrace 22 connects the front sub-frame 24 to the rear sub-frame 26 bybolt-on connections at a front end and a rear end. The motor, which isattached to the rear sub-frame 26, rotates out of the path of theintruding side member taking the inverter 12 with the motor. Theinverter protection brace 22 has a gusset 46 at the front end connectedto the front sub-frame 24 to load a beam section without overloadingattachment bolts. The gusset 46 is connected to the front sub-frame 24at a location outboard from a centerline of the vehicle. A portion ofthe inverter protection brace 22 load through the A-point boltconnections 56 a, 56 b contributes to deformation timing and shape ofthe front frame side members between the A-point bolt connections 56 a,56 b and the B-point bolt connections 34 a, 34 b. The gusset 46 rotatesbelow the front sub-frame 24 to delay loading of the inverter protectionbrace 22 and to delay bending of the front frame side members 50 a, 50 bto improve energy absorption of the front frame side members 50 a, 50 bduring frontal impacts. On the rear end, the inverter protection brace22 is attached by four bolts to the rear sub-frame 26 with an effectivehinge portion 48 forward of the rear bolt connections. The boltedconnection is connected to the rear sub-frame 26 at a location outboardof the centerline of the vehicle and inboard of the gusset 46 location.The gusset 46 connection is able to deform under the front sub-frame 24to delay loading of the inverter protection brace 22. Loading from theinverter protection brace travels through the rear sub-frame 26 to theA-point bolt connections 56 a, 56 b located on the pair of front sideframe side members 50 a, 50 b. The timing of this load, dictated by theinverter protection brace 22 front attachment kinematics, affect thefront side frame side members 50 a, 50 b bending between the A and Bpoint bolt connections 50 a, 50 b, 34 a, 34 b. The rear sub-frame 26deforms at the A-point bolt connections 56 a, 56 b. The inverterprotection brace 22 deforms adjacent the bolted connection at the rearend to form the safety cage 20 around the inverter 12 during frontalimpacts. The inverter protection brace 22 effectively creates the safetycage 20 around the inverter 12, as best seen in FIGS. 11A-11E during afrontal impact. Two configurations were studied for the inverterprotection brace 22: a strong dual pipe structure; and a stampedstructure with internal brace. The front attachment of the inverterprotection brace 22 to the front sub-frame 24 is gusseted to provide astrong connection through a knuckle or a gusset that allows fortranslational motion under the front sub-frame 24 to delay front frameside member collapse behind the A-point bolt connections 56 a, 56 b. Theinverter protection brace 22 has an elongate angled shape anglinginboard with respect to a centerline of the vehicle adjacent a rear end.The inverter protection brace 22 has a generally concave arcuate shapefrom front to rear. This inverter protection brace 22 is able totransfer approximately two hundred kilo-Newton (kN) of force rearwarduntil the rear sub-frame 26 attachment to the front side frame sidemembers 50 a, 50 b fails and the rear sub-frame 26 is released from theside frame under-members 32 a, 32 b.

Replacement of the internal combustion engine with a much smallerelectric motor removes the traditional load path through the firewallfor frontal impact. Removal of this load path results in additionalfront side frame side members 50 a, 50 b deformation and rear sub-frame26 motion which is directed toward the modules of the battery 16 in longrange electric vehicles. These batteries 16 must be protected againstrear sub-frame 26 attack. The addition of the ramps 28 a, 28 b to thevehicle side frame under-member 32 a, 32 b and/or rear sub-frame 26prevents this damage by directing intruding structures beneath thebatteries 16. The ramps 28 a, 28 b increase safe packaging volumeallowing the inclusion of a higher volume of cells for the battery 16 inthe vehicle. The higher volume of battery cells increases the range ofan electric vehicle. The ramps 28 a, 28 b allows a margin of safety foreven higher crash energies not included in government testing. Themotor/transmission is attached to the rear sub-frame 26 of the vehicle.The rear sub-frame 26 is able to move rearward into the vehicle sideframe under-members 32 a, 32 b and begin ramping down bolt-on ramps 28a, 28 b. These ramps 28 a, 28 b have multiple interface angles to allowsliding of the rear sub-frame 26 and attached structures (steering gear40, motor mount, bolts) down the angle and beneath the battery 16 formultiple frontal crash directions. The ramps 28 a, 28 b on the bodycabin 18 are welded or bolted to the vehicle side frame under-members 32a, 32 b. The ramps 28 a, 28 b are aligned with a chamfered surface 26 aof the rear sub-frame 26 to allow sliding. The pitch angle of the ramps28 a, 28 b is set such that crushing of the ramps 28 a, 28 b and therear sub-frame 26 is accounted for in the ramping trajectory, such thatattached structures of the rear sub-frame 26 passes below the batterystructure. The bolt-on type ramps 28 a, 28 b are illustrated in FIGS. 1,6, 7A-7E, 8A-8E, and 11A-11E which allows ramping on the interfaceshape. During some modes, the ramps 28 a, 28 b are designed to act asthe catching device 38 for the rear sub-frame 26 and attached structuresto improve energy absorption (EA) response of the vehicle system.

Referring now to FIGS. 1, 3, 4A-4D, 5A-5D, 11A-11E and 13A-13B, removalof the internal combustion (IC) engine load path through the firewallresults in more rear sub-frame 26 intrusion. In addition, the batterymodules 16 require protection from the intruding rear sub-frame 26.Using a deflection technique for the rear sub-frame 26 results in a lossof energy absorption (EA) as the rear sub-frame 26 structure slideseasily beneath the battery 16. This loss of energy absorption (EA) atthe rear sub-frame 26 results in more side member deformation andincreased load to the rocker. Both of which contribute to more intrusionto the body cabin 18 safety cage. The strong non-deformable ramps 28 a,28 b allow easy separation of the B-point bolt connections 34 a, 34 band sliding motion. Low energy absorption (EA) is realized, but goodtrajectory is accomplished. Locating the ramps 28 a, 28 b too close tothe rear sub-frame 26 results in quick separation of the rear sub-frame26 and an early loss of energy absorption (EA). Thus a space is createdusing the reinforcement bracket 30 a, 30 b positioned such that bucklingof a bottom wall 52 a of the side frame under-members 32 a, 32 b occursbetween the B-point bolt connection 34 a, b and a front edge 30 i, 30 jof the reinforcement brackets 30 a, 30 b, while a boundary strength of arearward wall of the reinforcement pockets 36 a, 36 b is defined by anoutboard reinforcing edge 30 k, 30 l of the bracket 30 a, 30 b. Thepocket 36 a, 36 b is able to temporarily restrain the rear sub-frame 26restoring a load path before slippage and energy absorption (EA) loss.

The reinforcement brackets 30 a, 30 b can serve a multi-purpose: i.e. anattachment point for the battery 16, an attachment point for the ramps28 a, 28 b and acting as an energy absorption (EA) pocket 36 a, 36 bfacilitator. Attaching the battery 16 and the ramps 28 a, 28 b to thereinforcement brackets 30 a, 30 b prevents relative movement between thetwo parts and provides a higher margin of safety. The reinforcementbracket 30 a, 30 b can be added to the vehicle side frame under-members32 a, 32 b. The reinforcement brackets 30 a, 30 b can be welded to thepair of side frame under-members 32 a, 32 b at a location rearward andinboard of a B-point attachment 34 a, 34 b of the rear sub-frame 26 tothe pair of side frame under-members 32 a, 32 b. The rear sub-frame 26can have a section which overlaps with the side frame under-members 32a, 32 b at the B-point bolt connections 34 a, 34 b as best seen in FIGS.13A-13B. During impact, each B-point bolt connections 34 a, 34 b isloaded as the rear sub-frame 26 moves rearward (as illustrated inphantom lines for t=44, t=68, and t=78). The location of thereinforcement brackets 30 a, 30 b is such that buckling of the bottomwall 52 a of the side frame under-members 32 a, 32 b starts to occur andthe pocket 36 a, 36 b is formed providing good energy absorption (EA) asthe side frame under-members 32 a, 32 b are deformed and the rearsub-frame 26 moves rearward. The reinforcement brackets 30 a, 30 bfacilitates formation and controls a deformation shape of the energyabsorption pocket 36 a, 36 b in the side frame under-members 32 a, 32 bforward of and outboard of the reinforcement brackets 30 a, 30 b duringa frontal impact for temporarily restraining the rear sub-frame 26 priorto the rear sub-frame 26 being released from a B-point bolt connections34 a, 34 b to the side frame under-members 32 a, 32 b and allowed toslide past the reinforcement bracket brackets 30 a, 30 b. After thepocket 36 a, 36 b fully deform, then the pocket back wall (shape andposition defined by the location of the bracket) 52 b tears releasingthe rear sub-frame 26 to slide past the reinforcement brackets 30 a, 30b. As best seen in FIG. 13A, a position of the back wall 52 b determinesan initiation strength of the back wall 52 a buckling for the pocket 36a, 36 b formation. An angular position of the reinforcement outboardback wall 52 b of the side frame under-members 32 a, 32 b determines astrength of the back wall 52 b and the deformed shape of the energyabsorption pockets 36 a, 36 b.

In this embodiment, the battery 16 and the ramps 28 a, 28 b both attachto the reinforcement brackets 30 a, 30 b. The reinforcement brackets 30a, 30 b defines an attachment for a battery 16 located rearward of thereinforcement brackets 30 a, 30 b, and an attachment for the ramps 28 a,28 b connected to a bottom wall 30 c, 30 d of the reinforcement brackets30 a, 30 b for directing rearward movement of the rear sub-frame 26beneath the battery 16. This construction prevents relative motionbetween the two structures increasing robustness. The reinforcementbrackets 30 a, 30 b includes bottom wall 30 c, 30 d and a pair ofupwardly extending sidewalls 30 e, 30 f, 30 g, 30 h on opposite sides ofthe bottom wall 30 c, 30 d, at least one sidewall 30 e, 30 g bending inan outboard direction at a forward end.

The reinforcement brackets 30 a, 30 b can be attached to the vehicleside frame under-members 32 a, 32 b by way of body welding. Both theramps 28 a, 28 b and the battery 16 can be attached in such a way thatrelative motion between the two structures is not allowed. Thereinforcement brackets 30 a, 30 b are positioned rearward on the sideframe under-member 32 a, 32 b connection to the rear sub-frame 26, suchthat the rear sub-frame 26 can move rearward before creating the pockets36 a, 36 b.

Referring now to FIGS. 1-2, 6, 8A-8E, and 11A-11E, to reestablish a loadpath between the rear sub-frame 26 and the side frame under-members 32a, 32 b after separation of the rear sub-frame 26 from the vehicle sideframe under-members 32 a, 32 b occurs, the steering gear 40 mounted totop side of the rear sub-frame 26 as best seen in FIG. 2 is used as aload path to push against an underbody structure, such as the ramp 28 aand/or the catching surface 38. The elimination of the internalcombustion engine removed the traditional load path between the frontalimpact barrier through the engine into the fire wall. This results inmore side member deformation and more rear sub-frame 26 rearward stroke.In order to prevent battery 16 damage in long range electric vehicles(EV) and to prevent body cabin 18 deformation, new load paths wereexplored. A frame structure system includes a deflection method to sendthe rear sub-frame 26 beneath the battery 16 that results in asubstantial load drop once deflection of the rear sub-frame 26 by theramps 28 a, 28 b occurs as overall interference between the rearsub-frame and vehicle frame is reduced. This load drop results inincreased body cabin 18 deformation as the remaining energy must beabsorbed by the remaining structure.

The catching surface 38 can be added to promote additional energyabsorption through locking of the catching surface 38 with respect tothe rear sub-frame 26, such that continued rearward motion of the lockedcatching surface 38 and the rear sub-frame 26 results in weld separationand crush of the side frame under-members 32 a, 32 b. By adding thecatching surface 38 on the deflection ramps 28 a, 28 b, the rearsub-frame 26 is slowed and energy absorption occurs as the locked rearsub-frame 26 and the catching structure 38 requires additional crush andweld separation of the side frame under-members 32 a, 32 b as thetemporarily locked structures move rearward helping to mitigate theeffects of the deflection on the body cabin 18. The ramps 28 a, 28 b canbe modified to include a standing flange or the catching surface 38 thatis able to engage the steering gear 40 mounted on a top side of the rearsub-frame 26, as best seen in FIG. 2, and catch protruding features fromthe steering gear 40 housing. The flange or catching surface 38 on theramps 28 a, 28 b is positioned in both the width and height position toprovide good overlap with the intrusion locus of the rear sub-frame 26for frontal impact modes (offset deformable barrier (ODB), frontal rigidbarrier (FRB), left angle rigid barrier (LARB)). As the rear sub-frame26 separates from the side frame under-members 32 a, 32 b, the rearsub-frame 26 moves rearward either crushing or sliding along the otherunder body components. As more sliding occurs, the reaction force dropsand more body cabin 18 intrusion results. By catching the rear sub-frame26 by interacting with the steering gear 40, motor mount, or additionalstructures the reaction load can be kept relatively high improvingloading efficiency and limiting load transfer through the side memberand toe-pan. An edge surface 28 of the ramps 28 a, 28 b is modified tocapture the steering gear 40 as the rear sub-frame 26 moves backwardtoward the battery 16.

Referring now to FIGS. 1, 10A-10B, 11A-11E and 14A-14B, to maximizeunderbody energy absorption, the tether 44 is used to hold the rearsub-frame 26 against ramps 28 a, 28 b to improve crushing trajectoryinstead of allowing easy slide and loss of the load path. In additionthis method increases the resulting normal force and resulting friction.The loss of energy absorption arises as a result of adding body ramps 28a, 28 b. A very strong tether 44 could conceptually control rearsub-frame 26 motion from initial impact and force additional X directionenergy absorption (EA) instead of allowing slip-off. Without a tether44, reliance is placed on rear sub-frame 26 interaction with theunderbody to keep contact. With a tether 44, more freedom for load angleis achieved which will allow better motion control. The tether 44 aidsto keep all moving parts in contact while prescribing additionalcrushing deformation and increasing friction. The steel tether 44modifies an existing noise-vibration (NV) and ride and handling brace toimprove the loading direction of the rear sub-frame 26 against theunderbody. The tether 44 is attached to the vehicle side frameunder-members 32 a, 32 b at two outboard attachment locations 54 a, 54 busing a bolt and reinforced bearing surface. The tether 44 is thenattached to the rear sub-frame 26 at two B-point inboard boltconnections 34 a, 34 b.

During frontal impact, the deformation of the rear sub-frame 26 rearwardbreaks the B-point bolt connections 34 a, 34 b from the side frameunder-members 32 a, 32 b. As the rear sub-frame 26 starts to slide downthe ramps 28 a, 28 b, the tether 44 holds the rear sub-frame 26 uprequiring additional crushing of both the side frame under-members 32 a,32 b and the rear sub-frame 26 resulting in greater energy absorption.The tether 44 is able to provide an upward force against the rearsub-frame 26 as the rear sub-frame 26 begins to slide down the ramps 28a, 28 b. This allows other energy absorption (EA) structures to performmore effectively. The tether 44 attaches at a rear portion of the rearsub-frame 26 and at outboard attachment locations 54 a, 54 b of a secondpair of side frame under-members 32 a, 32 b.

As best seen in FIGS. 14A-14B, the tether 44 is able to rotate, i.e.arrows 90 a, at the locations 54 a, 54 b of attachment to the side frameunder-members 32 a, 32 b. The tether 44 is angled forward from theout-board attachment locations 54 a, 54 b such that rearward motion ofthe rear sub-frame 26 slackens the tether 44 to a point where the tether44 has rotated to a position perpendicular to the vehicle axis. As thetether 44 rotates, there is a limited degree of displacement, i.e. someZ-axis displacement, i.e. see arrow 90 b, in FIG. 14B that is allowedfor the rear sub-frame 26. However, this Z-axis displacement is lessthan that demanded by the pitch set for the ramps 28 a, 28 b requiringadditional crush of the rear sub-frame 26 and a resulting higherfriction. In other words, the tether 44 slack from rotation is less thanthe increase in vertical displacement of the rear sub-frame 26 therebyrequiring additional crush of the rear sub-frame 26 and contactingcomponents before tether 44 separation. A combined trajectory path 92 ofthe rear sub-frame 26 along the ramps 28 a, 28 b restrained by thetether 44 extends through a progressively narrowing gap with decreasingclearance distances, where the clearance distances D₀>D₁>D₂. Theprogressively narrowing clearance gap requires additional crushing ofthe rear sub-frame 26 and resulting higher friction prior to separationof the tether 44.

Referring now to FIGS. 11A-11E, these simplified images are for IIHS, 35mph, 40% offset-deformable-barrier, test mode. Referring to FIG. 11A, asimplified side view of a front end of a motor vehicle illustrates theinverter 12, the side frame under-members 32 a, 32 b, the inverterprotection brace 22, the reinforcement brackets 30 a, 30 b, the ramps 28a, 28 b, the rear sub-frame 26, the front sub-frame 24, and the steeringgear 40 at time zero prior to a frontal impact with a barrier wall W. InFIG. 11B, the inverter 12, the side frame under-members 32 a, 32 b, theinverter protection brace 22, the reinforcement brackets 30 a, 30 b, theramps 28 a, 28 b, the rear sub-frame 26, and the steering gear 40 aredepicted at 44 milliseconds (ms) of time after a frontal impact. Theinverter protection brace 22 hits a wall, the front sub-frame 24 startsdeformation as the front attachment gusset 46 rotates under the frontsub-frame 24, and the energy absorption pockets 36 a, 36 b start to formas the rear sub-frame 26 is pushed rearward by the inverter protectionbrace 22 and initial bending of the front frame side-members 50 a, 50 bbetween the A and B point bolt bolt connectins 56 a, 56 b, 34 a, 34 b.FIG. 11C illustrates the inverter 12, the side frame under-members 32 a,32 b, the inverter protection brace 22, the reinforcement brackets 30 a,30 b, the ramps 28 a, 28 b, the rear sub-frame 26, and the steering gear40 at 68 milliseconds (ms) of time after a frontal impact. The rearsub-frame 26 approaches the ramp 28 a, 28 b, maximum front sub-frame 24crush occurs as the inverter protection brace 22 loads the walldirectly, the front frame side member 50 a, 50 b bends rearward of theA-point bolt connections 56 a, 56 b, a back side of pocket 36a, 36 breleases the B-point connections 34 a, 34 b of rear sub-frame 26, tether44 loading begins, and the rear sub-frame 26 slide along the ramps 28 a,28 b begins. In FIG. 11D, the inverter 12, the side frame under-members32 a, 32 b, the inverter protection brace 22, the reinforcement brackets30 a, 30 b, the ramps 28 a, 28 b, rear sub-frame 26, and the steeringgear 40 are depicted at 76 milliseconds (ms) of time after a frontalimpact. The tether 44 releases, rear sub-frame 26 is crushed to amaximum amount, and the rear sub-frame 26 slide along the ramps 28 a, 28b picks up as additional front frame side member 50 a, 50 b deformationoccurs. FIG. 11E illustrates the inverter 12, the side frameunder-members 32 a, 32 b, the inverter protection brace 22, thereinforcement brackets 30 a, 30 b, the ramps 28 a, 28 b, the rearsub-frame 26, and the steering gear 40 at 100 milliseconds (ms) of timeafter a frontal impact. Loading of the steering gear 40 starts, the rearsub-frame slide along ramps 28 a, 28 b approaches maximum, additionalload through the ramps 28 a, 28 b initiates the side frame under-members32 a, 32 b weld separation in area 60, and the inverter 12 shows minimaldamage.

In the force versus stroke curves of FIG. 12, the double dashed line 100shows the combination of the semi-strong front attachment inverterprotection brace 22 and the ramps, 28 a, 28 b welded directly to a frameunder-member providing a condition where ramping occurs early witheasily separating B-point bolt connections 34 a, 34 b of the rearsub-frame 26 from the side frame under-members 32 a, 32 b. Load from theinverter protection brace 22 is transferred through the A-point boltconnections 56 a,b and causes early front frame side members 50 a,bcollapse and EA loss shown by the lower bound of the cross hatching 110.A large drop in energy absorption (EA) occurs shown by the lowerboundary of the dashed horizontal line 108 due to easy slide. The solidline 102 illustrates the combination of the deformable front attachmentinverter protection brace 22, the bolted ramps 28 a, 28 b, thereinforcement brackets 30 a, 30 b providing a case with formation of theenergy absorption pockets 36 a, 36 b in the side frame under-members 32a, 32 b providing a large additional energy absorption (EA) area shownin cross hatching 106 below the dashed horizontal line 108. The sideframe under-member 32 a, 32 b deform to create the energy absorptionpockets 36 a, 36 b and subsequent tearing of the rear sub-frame 26 fromthe side frame under-members 32 a, 32 b. The cross hatching 110 showsthe improvement in early EA from delaying loading through the inverterprotection brace 22 by having a deformable front attachment allowingrotation of the brace under the front sub-frame. The single dashed line104 shows a high vehicle mass result with the combination of thedeformable front attachment inverter protection brace 22, thereinforcement brackets 30 a, 30 b forming the energy absorption pockets36 a, 36 b in the side frame under-members 32 a, 32 b, the ramps 28 a,28 b, the steering gear 38, and the tether 44. The cross hatching 110shows the improvement in early EA from delaying loading (and thereforedelayed front side frame side members 50 a, 50 b collapse) through theinverter protection brace 22 by having a deformable front attachmentallowing rotation of the inverter protection brace 22 under the frontsub-frame 24. The cross hatched area 106 corresponds to the additionalenergy absorption from initiation of the energy absorption pocketpockets 36 a, 36 b in the side frame under-members 32 a, 32 b by thereinforcement bracket 30 a, 30 b. The stippled area 112 corresponds tothe additional energy absorption attributable to the catching surface 38interacting with the steering gear 40 while supported in prolongedcrushing contact with the ramps 28 a, 28 b by the tether 44.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiments but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims, which scope is to be accorded the broadestinterpretation so as to encompass all such modifications and equivalentstructures as is permitted under the law.

1. A frame structure for a land vehicle having wheels to engage asurface over which the vehicle moves, an electric motor enabling thevehicle to be moved along the surface, the frame structure providingsupport for a vehicle body, where at least a portion of the framestructure changes shape in response to impact of the frame structurewith another body, the frame structure adapted to absorb energy fromfrontal impacts, the frame structure extending under a front portion ofthe vehicle body, the frame structure comprising: a front sub-frame anda rear sub-frame located below and in front of a pair of side frameunder-members; and an inverter protection brace extending between thefront sub-frame and the rear sub-frame for transferring energy from thefront sub-frame to the rear sub-frame during a frontal impact.
 2. Theframe structure of claim 1 further comprising: a gusset at a front endof the inverter protection brace for connecting the front sub-frame toload a beam section without overloading attaching bolts.
 3. The framestructure of claim 1 further comprising: a bolted connection at a rearend of the inverter protection brace to the rear sub-frame.
 4. The framestructure of claim 1 further comprising: A-point bolt connections of therear sub-frame to a pair of front frame side members located above therear sub-frame; and B-point bolt connections of the rear sub-frame tothe pair of side frame under-members, wherein loading from the inverterprotection brace travels through the rear sub-frame to the A-point boltconnections located on the pair of front frame side members, the rearsub-frame moves rearward and deforms at the A-point bolt connections, atleast one of the pair of side frame under-members buckles rearward ofthe B-point bolt connections for energy absorption during the frontalimpact.
 5. The frame structure of claim 4, wherein a portion of theinverter protection brace load through the A-point bolt connectionscontributes to deformation timing and shape of the front frame sidemembers between the A-point bolt connections and the B-point boltconnections.
 6. The frame structure of claim 4 further comprising: agusset at a front end of the inverter protection brace for connectingthe front sub-frame to load a beam section without overloading attachingbolts, wherein the gusset rotates below the front sub-frame to delayloading of the inverter protection brace and to delay bending of thefront frame side members to improve energy absorption of the front frameside members during frontal impacts.
 7. The frame structure of claim 1,wherein the inverter protection brace deforms adjacent a boltedconnection at a rear end to form a safety cage around an inverter duringthe frontal impact.
 8. The frame structure of claim 1 furthercomprising: a gusset at a front end of the inverter protection braceconnecting to the front sub-frame to load a beam section withoutoverloading attaching bolts, the gusset connected to the front sub-frameat a location outboard from a centerline of the vehicle; and a boltedconnection at a rear end of the inverter protection brace attaching tothe rear sub-frame, the bolted connection connected to the rearsub-frame at a location outboard of the centerline of the vehicle andinboard of the gusset location.
 9. The frame structure of claim 1further comprising: the inverter protection brace having an elongateangled shape angling inboard with respect to a centerline of the vehicleadjacent a rear end.
 10. The of claim 1 further comprising: the inverterprotection brace having a generally concave arcuate shape from front torear.
 11. A method of assembling structural members for absorbing energyfrom frontal impacts of a frame structure for a land vehicle havingwheels to engage a surface over which the vehicle moves, an electricmotor enabling the vehicle to be moved along the surface, the framestructure providing support for a vehicle body, where the framestructure changes shape in response to impact of the frame structurewith another body, the frame structure extending under a front portionof the vehicle body, the method comprising: locating a front sub-frameand a rear sub-frame below and in front of a pair of side frameunder-members; and connecting an inverter protection brace extendingbetween the front sub-frame and the rear sub-frame for transferringenergy during a frontal impact.
 12. The method of claim 11 furthercomprising: connecting a gusset at a front end of the inverterprotection brace to the front sub-frame to load a beam section withoutoverloading attachment bolts.
 13. The method of claim 11 furthercomprising: bolting the inverter protection brace at a rear end to therear sub-frame.
 14. The method of claim 11 further comprising:connecting the rear sub-frame to a pair of front frame side memberslocated above the rear sub-frame at A-point bolt connections; andconnecting the rear sub-frame to the pair of side frame under-members atB-point bolt connections, wherein loading from the inverter protectionbrace travels through the rear sub-frame to the A-point bolt connectionslocated on the pair of front frame side members, the rear sub-framemoves rearward and deforms at the A-point bolt connections, at least oneof the pair of side frame under-members buckles rearward of the B-pointbolt connections for energy absorption during the frontal impact. 15.The method of claim 14 further comprising: loading a portion of theinverter protection brace through the A-point bolt connections tocontribute to deformation timing and shape of the front frame sidemembers between the A-point bolt connections and the B-point boltconnections.
 16. The method of claim 14 further comprising: connecting agusset at a front end of the inverter protection brace to the frontsub-frame to load a beam section without overloading attachment bolts;and rotating the gusset below the front sub-frame to delay loading ofthe inverter protection brace and delay bending of the front frame sidemembers to improve energy absorption of the front frame side membersduring frontal impacts.
 17. The method of claim 11 further comprising:deforming the inverter protection brace adjacent a bolted connection ata rear end to form a safety cage around an inverter during the frontalimpact.
 18. The method of claim 11 further comprising: connecting theinverter protection brace to the front sub-frame with a gusset at afront end to load a beam section without overloading attaching bolts,the gusset connected to the front sub-frame at a location outboard froma centerline of the vehicle; and connecting the inverter protectionbrace to the rear sub-frame with a bolted connection at a rear end, thebolted connection connected to the rear sub-frame at a location outboardof the centerline of the vehicle and inboard of the gusset location. 19.The method of claim 11 further comprising: providing the inverterprotection brace with an elongate angled shape; and angling the inverterprotection brace inboard with respect to a centerline of the vehicleadjacent a rear end.
 20. The method of claim 11 further comprising:providing the inverter protection brace with a generally concave arcuateshape from front to rear.
 21. A frame structure adapted to absorb energyfrom frontal impacts, the frame structure extending under a frontportion of a vehicle body, the frame structure comprising: a frontsub-frame and a rear sub-frame located below and in front of a pair ofside frame under-members; and an inverter protection brace extendingbetween the front sub-frame and the rear sub-frame for transferringenergy from the front sub-frame to the rear sub-frame during a frontalimpact.
 22. The frame structure of claim 21 further comprising: a gussetat a front end of the inverter protection brace connecting to the frontsub-frame to load a beam section without overloading attaching bolts;and a bolted connection at a rear end of the inverter protection braceto the rear sub-frame.
 23. The frame structure of claim 21 furthercomprising: A-point bolt connections of the rear sub-frame to a pair offront frame side members located above the rear sub-frame; and B-pointbolt connections of the rear sub-frame to the pair of side frameunder-members, wherein loading from the inverter protection bracetravels through the rear sub-frame to the A-point bolt connectionslocated on the pair of front frame side members, the rear sub-framemoves rearward and deforms at the A-point bolt connections, at least oneof the pair of side frame under-members buckles rearward of the B-pointbolt connections for energy absorption during the frontal impact. 24.The frame structure of claim 23, wherein a portion of the inverterprotection brace load through the A-point bolt connections contributesto deformation timing and shape of the front frame side members betweenthe A-point bolt connections and the B-point bolt connections.
 25. Theframe structure of claim 23 further comprising: a gusset at a front endof the inverter protection brace connecting to the front sub-frame toload a beam section without overloading attaching bolts, wherein thegusset rotates below the front sub-frame to delay loading of theinverter protection brace and delay bending of the front frame sidemembers to improve energy absorption of the front frame side membersduring frontal impacts.
 26. The frame structure of claim 21, wherein theinverter protection brace deforms adjacent a bolted connection at a rearend to form a safety cage around an inverter during the frontal impact.